Lubricants for metalworking operations



United States Patent O 3,526,596 LUBRICANTS FOR METALWORKING OPERATIONS Bernard H. Kress, Lafayette Hill, and Donald E. Alexander, Wayne, Pa., assiguors to Quaker Chemical Corporation, Conshohocken, Pa., a corporation of Pennsylvania No Drawing. Filed June 5, 1968, Ser. No. 734,572 Int. Cl. Cn 3/04, 3/18 US. Cl. 252-495 11 Claims ABSTRACT OF THE DISCLOSURE The invention relates to synthetic lubricants used at very high temperatures in the process of shaping and working metals while they are heated to temperatures at which they are malleable. The lubricants are applied as a film to the surfaces of the work elements which operate on the heated metals, for example on the working or finishing rolls of a continuous hot-roll steel mill.

The polyol esters of fatty acids having 12 to 22. carbon atoms, or mixtures thereof, are excellent lubricants for hot metal working operations. The preferred polyols have 2 to 12 hydroxy groups, including for example, pentaerythritol or polymers thereof, trimethylol ethane, trimethylol propane, and glycols containing from 2 to 40 carbon atoms. Also included in these polyols are inositol, mannitol, sorbitol, glucose, sucrose, trirnethylol benzene, hexamethylol benzene, methyl glucosides, glycerol, polyglycerols and, in fact, any polyol capable of reacting with at least two selected fatty acid molecules to form a minimum of a diester.

Other lubricant compositions useful for hot working of metals are acid phosphate esters of ethylene oxide condensates. These condensates may include those with fatty alcohol, phenolic and substituted phenolic, oxo process alcohol and acetylenic alcohol hydrophobes. The hydrophilic portion may include chains of ethylene glycol moieties, propylene glycol moieties or those containing a mixture thereof.

Other lubricants for hot metal operations are fatty acid modified alkyd resins. These include condensation products of fatty acids, usually mixtures, polyol or polyols, and dicar-boxylic acids. These include phthalic, isophthalic, terephthalic, maleic, fumaric, tetrahydrophthalic, succinic, adipic, azelaic, sebacic acids, and condensation products of maleic anhydride with various compositions such as rosin.

Oxyalkylene copolymers are also useful lubricants for hot metal operations. These copolymers for example are formed by interaction between ethylene oxide and propylene oxide, either as random copolymer, or as grafts. Both of these classes maybe formed by reacting the oxide with a compound containing a reactive hydrogen such as butanol or similar composition.

FIELD OF THE INVENTION This invention relates to compositions of matter for use as lubricants at extremely high temperatures in the working and shaping of heated malleable metals and alloys. The synthetic lubricants are particularly useful in shaping steel products, such as steel plate, bar, strip, sheet, rod, beams and rails, and particularly in continuous hotstrip mills. The lubricants are also useful in hot working of copper, brass, aluminum, magnesium, and titanium.

DESCRIPTION OF THE PRIOR ART Modern lubricants are frequently required to function at temperatures above 400 R, where known mineral oils deteriorate rapidly, become corrosive, and volatilize,

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thereby becoming useless for their intended purpose. Available synthetic base oils, such as esters, ethers, silicones or hydrocarbon polymers, often undergo thermal and oxidative degradation under these extreme conditions, resulting in sludge and deposit formation, viscosity change, resulting in sludge and deposit formation, viscosity change, discoloration, increased corrosivit'y, and other undesirable changes. Attempts to correct these deficiencies by conventional methods have been unsuccessful because of the extreme working conditions; for example, addition of an antioxidant to reduce deterioration may cause increased corrosion, or addition of an antiwear agent might decrease stability. Furthermore, attempts to remedy the new deficiencies frequently compound the problem by causing increased sludging, etc. Therefore, available information regarding mineral oil formulations is of little aid in developing successful synthetic lubricants for use at temperatures above 400 F.

Hitherto no satisfactory lubricants have been available for hot-rolling of steel products. Therefore no lubricants have been used at all. The advent of present-day high speed hot strip mills, larger steel slabs, and continuous casting operatons has created an urgent need for hot mill lubricants in order to minimize surface defects in the finished products and prolong the life of the work and backup rolls used in rolling the steel. The difliculty in providing suitable lubricants is apparent when it is realized that continuous hot mill operations are carried out at temperatures ranging from 1600 F. to about 2100 F.

In a typical continuous steel hot-rolling mill the train may consist of a roughing scalebreaker, four or more four-high roughing stands, a finishing scalebreaker, and six or more tandem four-high finishing stands. Driven table rolls convey the steel from stand to stand. Steel slabs are conveyed to the train at temperatures ranging from 2000 to 2400 F. The steel slabs are rolled to desired thickness and the rolled product is cut in desired lengths or coiled as a single piece. The four-high finishing stands each consist of a pair of driven working rolls between which the steel is worked and reduced in thickness. The working rolls coact with backup pressure rolls which provide added support to the work rolls and secure greater reduction per pass. A description of such continuous hot-strip mill is given in The Making, Shaping and Treating of Steel, 8th ed. 1964, published by US. Steel Corp. pages 894-902.

GENERAL STATEMENT OF THE INVENTION The present invention provides synthetic lubricants that for the first time can be used particularly very effectively for steel hot-strip operations. The lubricants of the present invention are applied in liquid condition or in water despersions to the metal working elements, such as the working rolls of a hot-strip steel mill, by means of any available equipment to produce a uniform continuous film on the surface of the working rolls. The liquid lubricant may be supplied by means of spray equipment to both the top and bottom backup rolls, on the exit side of the stand, to permit the lubricant to be carried into the bite between the backup and work rolls. At this point, the lubricant is evenly spread across the face of the backup and work rolls. The lubricant may be applied on one or more stands of the finishing train. The lubricant application is generally confined to the pivot stands on the finishing train or those stands most susceptible to roll wear. If desired the lubricant may also be used on the roughing mills. In actual mill operations it has been found advantageous to keep the work rolls free of lubricant prior to the entrance of a bar into the particular stand on which the lubricant is being applied. If the lubricant is present on the work rolls, then the proper bite of the bar does not take place and cobbling of the strip may result because the coeflicient of friction is reduced through the use of a lubricant and there is a tendency for the mill to throw slack.

DESCRIPTION OF PREFERRED EMBODIMENTS The following compositions are useful as lubricants in the shaping or working of metals, such as steel and the like, which are heated to their malleable temperatures.

I have discovered that the polyol esters of fatty acids having 12 to 22 carbon atoms, or mixtures thereof, are excellent lubricants for hot metal working operations. The preferred polyols have 2 to 12 hydroxy groups, including for example, pentaerythritol or polymers thereof, trimethylol ethane, trimethylol propane, and glycols containing from 2 to 40 carbon atoms. Also included in these polyols are inositol, mannit-ol, sorbitol, glucose, surcrose, trimethylol benzene, hexamethylol benzene, methyl glucosides, glycerol, polyglycerols and, in fact, any polyol capable of reacting with at least two selected fatty acid molecules to form a minimum of a diester.

Among the fatty acids useful for making the polyol esters are:

(A) Natural fatty acids both saturated and unsaturated containing 12 to 22 carbon atoms including the following acids: lauric, lauroleic, myristic, myristoleic, arachidic, eicosapolyenoic, pentadecanoic, palmitic, palmitoleic, margaric, stearic, oleic, linoleic, eicosenoic, behenic, ricinoleic, dihydroxyl stearic, licanic, elaeo-stearic, docosenoic, docosapolyenoic, tallow fatty acids which are mixtures of saturated and unsaturated fatty acids having 16 to 18 carbon atoms, and tall oils.

Also, included are any isomers of the above acids such as elaidic acid. Any of these acids may be used in admixture to obtain the desired esters. Smaller amounts of rosin acids may also be used along with the fatty acids. Neo-acids or iso-acids, such as neopentanoic, neo-decanoic, neotridecanoic acids and other similar acids obtainable from oxidation of x0 processes compounds are also included in this group. Those acids obtainable by oxidation of alpha olefines and alphaolefins derived alcohols are also useful. Finally, synthetic fatty acids obtainable from petroleum products as well as so-called naphthenic acids may be used.

The esters of the fatty acids and polyol may be prepared by any known procedure commonly used for preparation of these esters. These include heating in a still by direct thermal fusion, with and without catalysts. Such catalysts may be acids, Lewis type acids, metallic oxides, metallic hydroxides, and the like. The water of the reaction is then suitably removed. Azeotropic removal of water of reaction, distillation of water of reaction under vacuum, and removal of water of reaction by gas sparging may be used. The ester products are preferably used directly in anhydrous condition as lubricants for hot metal working operations. Mixture of esters may be used or they may be diluted with mineral oil fractions or other solvents for special applications. In addition, such parting aids such as silica, fine clay, fly ash, fullers earth, graphite, talc, and the like, may be used in conjunction with the lubricant particularly when used in metal casting and forging operations.

Other lubricant compositions useful for hot working of metals are:

(B) Acidic phosphate esters of ethylene oxide condensates. These condensates may include those with fatty alcohol, phenolic and substituted phenolic, oxo process alcohol and acetylenic alcohol hydrophobes. The hydrophillic portion may include chains of ethylene glycol moieties, propylene glycol moieties or those containing a mixture thereof. The acid portion is contributed by an unesterified phosphoric acid group and may be neutralized with ammonia, amine, an alkali metal hydroxide, an alkaline earth hydroxide or unneutralized.

(C) Fatty acid modified alkyd resins. These include condensation products of fatty acids, usually mixtures, polyol or polyols, and a dicarboxylic acids. These include 4 phthalic, isophthalic, terephthalic, maleic, fumaric, tetrahydrophthalic, succinic, adipic, azelaic, sebacic acids, and condensation products of maleic anhydride with various compositions such as rosin.

(D) Oxyalkylene copolymers. These compolymers for example are formed by interaction between ethylene oxide and propylene oxide, either as random copolymer, or as grafts. Both of these classes may be formed by reacting the oxide with a compound containing a reactive hydrogen such as butanol or similar composition.

The products of the aforementioned groups B, C and D can be applied as lubricants in conjunction with mineral oil and/ or solvents. Water may also be used as diluent with the products of groups B and D, as well as other solvents.

The following are specific illustrative examples particularly useful as lubricants in continuous steel hot-strip mills. The component parts given in the examples are by weight:

EXAMPLE 1 Parts Tallow fatty acids 840 Trimethylol ethane EXAMPLE 2 Parts Oleic acid 1120 Pentae'rythritol i 136 Toluene sulfonic acid 0.1 Xylene 50 This mixture was heated at temperatures of up to 400 F. while water of reaction was distilled off azeotropically, the xylene layer being returned continuously. When 70 parts of Water of reaction had been removed, the xylene was evaporated in vacuo leaving a yellow liquid product which was essentially tetraoleate of pentaerythritol.

EXAMPLE 3 Parts Tall oil-distilled 855 Trimethylol propane Boron trifluoride etherate 0.1

This mixture was heated to 325 F. and maintained at this temperature while water of reaction was distilled off. When 52 parts of water had been removed, vacuum being used at the end of the reaction, the product formed was a yellow oil which was essentially tritallate of trimethylol propane.

EXAMPLE 4 Parts Tall oil heads 1000 Glycerine 92 This was heated at 500-525 F. with nitrogen sparge to assist distillation of water. When about 50 ml. of water of reaction had formed the reaction was stopped yielding a deep brown liquid which was essentially tritallate of glycerine.

EXAMPLE 5 Parts Red oil (oleic acid) 560 Polyethylene glycol 600 p-Toluene sulfonic acid oil 0.1

This mixture was heated at 325 F. until 35 parts of water of reaction had been removed. A light brown oily liquid resulted which was essentially polyethylene glycol dioleate.

This mixture was heated at 525 F. until 85-90 parts of water of reaction had been removed. The reaction product was a somewhat viscous yellow brown liquid which was essentially the ester of dipentaerythritol and coconut fatty acids.

The lubricants of the present invention are useful in the continuous production of hot-rolled fiat steel plate, strip, sheet and bars and other metals and alloys such as copper, brass, aluminum, magnesium, titanium, etc. The lubricants are also useful in other hot metal working operations such as extrusion, shaping, forging, continuous casting, etc. The lubricants have the property of wetting and spreading on the surface of the working elements as well as on the metal being worked to provide a boundary medium between the surface of the working elements and the metal being worked.

According to this invention specific lubricants are provided with predetermined viscosities, pour points, and lubricating properties for use on all types of hot strip operations. These lubricants ensure excellent wetting on hot mill surfaces and lay down a film which will remain on the surface of the rolls and provide a boundary cushion to prevent oxide formation or buildup on the surface of work rolls and backup rolls. The lubricants perform their lubricating function and then flash off preventing any residues from remaining on the strip surface. The molecular film remains on the strip for sufiicient time to provide some lubrication to the succeeding stand.

The present invention results in many advantages and reduces the cost of equipment maintenance in hot strip mills. The use of the lubricants of the present invention in working steel bars at temperatures ranging from 1600 F. to 2100 F. offers the following advantages:

(1) Provides for increased roll life on both backup and work rolls. Present-day increased mill speeds produce greater friction and increased roll wear.

(2) Greatly reduces mill down time because of fewer roll changes, thus providing for increased production. Welding of scale to surface of the rolls is reduced.

(3) Provides for improved hot rolled strip quality such as better surface finish. The tremendous friction which develops between the strip and the work rolls tends to cause tears or defects in the surface of the metal which is reduced by the lubricant.

(4) Provides for improved pickled srtip (reduces scale drags, rolled-in scale, etc.). With reduced rolled-in scale, pickling speeds could be increased.

(5) Reduces the amount of metal removal from the roll surface during roll dressing of a used roll (backup and work rolls). This would provide for more tonnage per set of rolls.

(6) Permits lower loads on hot mill (lower power consumption).

(7) Provides savings in mechanical labor man hours because of infrequency in roll changes. (Assembly and disassembly of work roll and backup bearings.)

(8) Provides for a reduction in work roll inventory necessary to maintain work rolls because of frequency of change.

There are other additional advantages, such as less acid.

consumption during pickling. Overall high quality of the product is achieved and also greater yield because of reduced hot mill defects. A porous surface, caused by worn work rolls, is much more susceptible to entrapment of contaminants which end up as rolled-in dirt. The cost of roll replacement is thus greatly reduced.

We claim:

1. The process of mechanically working a hot malleable metal which comprises the steps of heating said metal to a malleable state, applying working pressure on the surface of said metal with a working element having a working surface acting on said metal while at a temperature from about 1600" F. to about 2100 F., supplying a synthetic liquid organic lubricant consisting essentially of a polyol ester of fatty acid, said polyol having 2 to 12 hydroxy groups and said fatty acid having 12 to 22 carbon atoms to said working surface and uniformly spreading the lubricant on said working surface prior to contacting said working surface with said heated malleable metal to provide a boundary medium at the interfaces of said working surface and the surface of the said metal.

2. The process of claim 1 wherein the metal is steel.

3. The process of claim 1 wherein the lubricant is a pentaerythritol ester of a fatty acid having 12 to 22 carbon atoms.

4. The process of claim 1 wherein the lubricant is tritallowate of trimethylol ethane.

5..The process of claim 1 wherein the lubricant is tetraoleate of pentaerythritol.

6. The process of claim 1 wherein the lubricant is tritallate of trimethylol propane.

7. The process of claim 1 wherein the lubricant is tritallate of glycerine.

8. The process of claim 1 wherein the lubricant is polyethylene glycol dioleate.

9. The process of claim 1 wherein the lubricant is the ester of dipentaerythritol and coconut fatty acids.

10. The process of claim 1 wherein the lubricant is a fatty acid modified alkyd resin.

11. The process of claim 1 wherein the lubricant is applied as an aqueous dispersion.

References Cited UNITED STATES PATENTS 2,744,871 5/1956 Williams et al. 25256 2,755,250 7/1956 Watson et al. 25256 2,808,421 10/1957 Brokaw 25256 2,958,706 11/ 1960 Hurwitz et a1 25256 3,029,204 4/1962 Matuszak et al 25256 3,048,608 8/ 1962 Girard et al. 25256 3,130,159 4/1964 Stedt 25256 3,256,211 6/1966 Bailey et al. 25252 3,282,971 11/ 1966 Metro et al. 25256 3,310,489 3/ 1967 Davis 252-495 FOREIGN PATENTS 739,998 8/1966 Canada.

OTHER REFERENCES Cohen et al.: Aliphatic Esters, I and E Chem. 45, 8, pp. 1766-1774.

DANIEL E. WYMAN, Primary Examiner J. M. HICKEY, Assistant Examiner U.S. Cl. X.R. 25249.8, 52, 56 

